Magnetic sheet classifier

ABSTRACT

A magnetic classifier for flat ferrous sheets comprising upper and lower conveyors, the lower conveyor having a sheet-receiving portion and a sheet-exiting portion and an intermediate portion wherein a plurality of electromagnets are supported along a curved path longitudinally of the reach of the belt of the lower conveyor. The belt reach follows this curved path and, when the electromagnets are energized, the sheet is attracted to the belt reach and longitudinally curved to correspond to the curvature of the path. The curvature of the path is in an amount that would not bend the sheet beyond its elastic limit, so that the sheet will resume its flat condition when it is moved by the belt reach beyond the curved path.

. United States Patent 1191 3,814,243 Miller 1 June 4, 1974 [54] MAGNETIC SHEET CLASSIFER FOREIGN PATENTS OR APPLICATIONS [751 hlvemoh Paul Miller, warren, Ohio 216,422 12/1960 Austria 198/41 Assignea: w United Inc. YoungstownI 451,585 8/l930 Great Brltum 209/223 Ohio Primary Examiner-Robert Halper [22] F'led: May 1972 Attorney, Agent, or Firm-Michael Williams [21] Appl. No.: 251,938

, [57] ABSTRACT [52] US. Cl 209/223 A, 198/41, 271/63 A A magnetic classifier for flat ferrous sheets comprising [51] Int. Cl B03d 1/22 upper and lower conveyors, the lower conveyor hav- [58] Field of Search,, 209/214, 215, 223 R, 223 A, ing a sheet-receiving portion and a sheet-exiting por- 209/507 AR; 198/41, 216; 271/63 A tion and an intermediate portion wherein a plurality of I electromagnets are supported along a curved path lon- [56] References Cit d gitudinally of the reach of the belt of the lower con- UNITED STATES PATENTS veyor. The belt reach follows this curved path and, g when the electromagnets are energized, the sheet is gz l 2 attracted to the belt reach and longitudinally curved 1,130,648 3/1915 11116661113111: 1:: 209/223 A to correspond to the Curvature f the Path The 1,218,916 3/1917 Weatherbym. 209/214 x We of the P is in an amount that would not bend 2,303,526 12 1942 Cummings 209 223 A x the sheet beyond its elastic limit, so that the sheet will 2,340,797 12/1944 Cummings.... 271/63 A resume its flat condition when it is moved by the belt 2,661,092 l2/l953 lnjesni 209/223 R reach beyond the curved path, 2,897,952 8/1959 Buccione l98/4l 2,947,429 8/1960 Buccione 271/63 A x 7 Claims, 4 ra ing Figures MAGNETIC SHEET CLASSIFIER BACKGROUND AND SUMMARY Magnetic classifiers for ferrous sheets are known in the prior art, an illustrative example being found in US. Pat. No. 2,176,784. Classifiers of this type include upper and lower conveyors, with magnetic means to divert certain sheets from one conveyor to the other. In order to insure positive action to divert such sheets, a stationary or pivoted deflector or flap gate is normally positioned at the point of sheet diversion to positively deflect the desired sheets. The pivoted deflector gates are normally controlled by a timing device which is preset to move the gate just as the selected sheet arrives in advance of the gate. The gates are usually mechanically moved about their pivots and both stationary and pivoted gates are relatively heavy and of special shape and construction, and therefore add expense to the apparatus and also limit the speed at which sheets may be classified.

My improved magnetic classifier eliminates the need for a deflector or flap gate and thus not only reduces cost and maintenance but also permits an increase in speed of sheet classification. According to my invention, sheets are successively delivered to the upper reach of the belt of the lower conveyor and are held to movement with such reach by magnetic means. In the area of sheet classification, the belt of the lower conveyor is moved along a curved path and electromagnets are disposed beneath the reach and, when energized, attract and hold the sheet to the reach. The curved path enables the belt of the lower conveyor to diverge considerably from the lower reach of the belt of the upper conveyor beyond the area of classification, and further magnetic means are provided to hold the sheet to the belt of the lower conveyor until the sheet reaches the exit end of the conveyor. Although the sheet is curved longitudinally as it passes along the curved path, no harm is done to the sheet since the curvature of the path is chosen so that the sheet is not bent beyond its elastic limit.

DESCRIPTION OF THE DRAWINGS In the drawings accompanying 'this specification and forming a part of this application, there is shown, for purpose of illustration, an embodiment which my invention may assume, and in these drawings:

FIG. 1 is a longitudinal sectional section through a presently preferred embodiment of my invention, the apparatus being shown more or less schematically,

FIG. 2 is an enlarged, broken and fragmentary view of an end view of the apparatus as viewed from the left end of FIG. 1,

FIG. 3 is an enlarged fragmentary side view of the apparatus, and

FIG. 4 is a broken top plan view of the apparatus shown in FIGS. 2 and 3, the belt tensioning means being omitted in the interest of clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENT The sheet classifier of the present invention is particularly suited to sort metal sheets in accordance with gauge characteristics and although the description will be largely confined togauge-sorting of sheets, it will be understood that sheets may also be classified in accordance with surface defects or other objectionable characteristics.

As an example of one use of my invention, a long strip of metal, such as in coil form, is fed to a shear. At a suitable point prior to shearing of the strip into sheets, the gauge characteristics of the strip is determined, such as by an electro-limit gauge which is commercially available. As the strip passes through this gauge, the off-gauge characteristics (beyond tolerance limits) are impressed on electrical circuits in known manner, to operate the magnetic gate of my invention at the proper time. The strip is then sheared and the sheared sheets are deposited in successive manner upon the entrance portion of my improved classifier.

For the purpose of the present disclosure, the sheets are classified into two groups, one of which will hereinafter be termed OK and the other of which will be termed Off-Gauge with the understanding that the latter term designates sheets beyond the tolerance limits of a desired gauge.

If the sheets are to be classified for other defects, such as surface defects, wavy edges or the like, such defects may be visually observed by an operator who would manually control the electric circuits which affect my improved classifier.

Referringparticularly to FIG. 1, the sheet classifier of my invention comprises a top magnetic conveyor 10 and a bottom magnetic conveyor 11. The top conveyor includes a flexible belt 12 (shown in dot-dash lines for purpose of clarity) which is trained over a pair of spaced rolls 14, 15, and over rolls 16, 17 which are part of a slack take-up device 18 (see also FIG. 3). The lower reach of the belt travels under sets of magnets which in the present embodiment are shown as four sets of magnets 20, 21, 22 and 23, each set being separately mounted so that it may be individually repaired or replaced. The magnets 25 in sets 20, 21 and 22 may be permanent magnets although it is preferable to use electromagnets which are constantly energized during the operation of the sheet classifier. The magnets 26 in set 23 are energized only at certain times, as will be explained later.

The bottom magnetic conveyor 11 is considerably longer than the upper conveyor 10 and includes a sheet receiving portion 30 for receiving successive sheared sheets to be classified. The bottom conveyor includes a flexible belt 31 (also shown in dot-dash lines for clarity) which is trained over a pair of spaced rolls 32, 33, and over rolls 34, 35 which are part of slack take-up device 36 (see also FIG. 3).

Each of the belts l2 and 31 may be formed of any suitable flexible material. It has been found that a belt formed of canvas and covered with an oil resistant material is suitable for the purpose.

The upper reach of the belt 31 travels over magnets and, as seen in FIG. 1, the sheet receiving portion preferably inclines upwardly toward the roll 15 of the upper conveyor, to form a throat 40, and then merges with a curved portion 41 and then preferably inclines downwardly at the sheet exit portion 42. The lower reach of the upper conveyor belt is disposed in closely spaced relation to the upper reach of belt 31 at the entrance tothe throat 40 and inclines upwardly to gradually widen the spacing between the belts. As seen in FIG. 1, the belt 12 in the vicinity of the magnet sets 20, 21 inclines slightly upwardly.

The sheet receiving portion 30 of the lower conveyor has spaced rows of magnets 45, 46, 47, 48, 49 and 50, the spacing between the rows being slightly less than the minimum length of sheets to be classified so that each sheet is always subject to magnetic attractionto hold it to the upper conveyor reach and thus prevent slipping of the sheet along the reach. The magnets in rows 45 through 50 may be permanent magnets, but preferably are electromagnets which are energized at all times that the sheet classifier is being operated. Small rollers 51 are mounted between the rows of magnets to provide support for the upper reach of the belt 31.

Rows of magnets 55, 56 and 57 are disposed crosswise of and under the upper reach of the belt 31 at the sheet exit portion 42 of the bottom conveyor to hold the sheets against slipping on the belt, and small rollers 58 are provided'to support the belt.

At the curved portion 41 of the bottom conveyor, a plurality of rows of electromagnets 60 are disposed to follow the curvature and thus provide a curved support for the upper reach of the belt 31. Nine rows of magnets 60 are shown in FIG. 1, but this number may be varied. v

The belts 12 and 13 are driven at the same speed and in the same direction (as. indicated by the arrows in FIG. 1). Sheared sheets, as before'described, are deposited successively on the entrance portion 30 of the classifier and move with the upper each of the belt 31 to the throat 40. A sheet at this point may remainon the belt 31 or be attracted to the belt 12, depending on whether it is Off-Gauge or OK gauge. As before mentioned, the electro-limit gauge has already determined gauge characteristics of the strip before shearing and such characteristics are impressed on electrical circuits in timed relation with movement of the shear sheets, so that when an Off-Gauge sheet reaches the throat area 40, the electromagnets in set 23 of the upper conveyor are energized, whereas the sets of magnets 60 of the bottom conveyor are not energized. Therefore, the Off-Gauge sheet is attracted to the lower reach of the belt 12 and carried thereby to the adjoining end of a conveyor 65 for delivery to a reject pile or to another magnetic separator for further classification.

In the event the sheet is of OK gauge, the sets of electromagnets 60 of the bottom conveyor are energized, whereas the electromagnets in set 23 of the upper conveyor are not energized. Therefore, the sheet is held to theupper reach of the belt 31 and carried thereby to the adjoining end of a conveyor 66 for delivery to a pile or to another magnetic separator for further classification.

As before pointed out, the sets of magnets 60 in the curved portion 41 of the lower conveyor cause the upper reach of the belt 31 to curve correspondingly. The amount of curvature is such that the sheet attracted to the upper reach of belt 31 at this point is correspondingly curved, but not beyond its elastic limit. This is an important feature in view of the high speeds at which'the belts l2 and 31 are driven, since it eliminates the necessity of a deflector gate between the belts at the exit end of the magnetic separator.

FIGS. 2 through 4 disclose a practical machine embodying my invention. This machine includes uprights 70 for supporting the structure from the floor. Side beams 71 are rigidly connected to the uprights, each beam having a flange which provides support for the magnets in the receiving, curved and exit portions 30,

41 and 42, respectively, of the lower conveyor 11.

The upper conveyor 10 is suspended from a pair of cross beams 72 which are carried by the upper ends of the supports for vertical adjustment. Extending downwardly at opposite ends of each cross beam 72 are pairs of cars 73 between which are pivoted lugs 74. Extending downwardly from each lug is a rod, the lower endof which forms part of a screw jack 75. In the presently disclosed embodiment, all four screw jacks are connected for. simultaneous operation to raise or lower the upper conveyor. As seen'in FIG. 4, shafts 76, 76 extend crosswise of the beams 72, flexible couplings 77 at opposite ends ofeach shaft connect to the jack screws associated with such shaft ends. Extending crosswise of the upper conveyor is a shaft 78 having flexible couplings 79 at opposite ends. The couplings 79 connect to shafts 80 of respective gear boxes 81, such boxes each containing miter gears (not shown) so that other shafts 82 extending from the gear boxes may be connected to the adjoining screw jacks. It will be noted that operating stubs 83 are located at the four corners of the machine (as viewed in top plan in FIG. 4) so that an operating crank may be applied to any stub to effect vertical adjustment of the upper conveyor.

The shaft 85 of upper conveyor roll 14 is carried in bearings 86 which are connected to support beams 87 carried by and extendingdownwardly from the crossbeams 72. The shaft 88 of upper conveyor roll 15 is similarly carried in bearings 89 which are connected to the opposite end of the support beams 87. F l6. 4 schematically shows the'shaft 85 rotatably connected to a gear reducer 90, with the latter driven by a suitable motor 91.'A similar drive may be provided for the bottom conveyor 11. v

As seen in FIG. 4, the magnet sets 20, 21, 22 and 23 are each carried by channels 92, the webs 93 at the opposite ends of each channel being bolted to the support beams 87. Thus, any set of magnets may be individually removed from the machine for repair or replacement. The magnets inthe bottom conveyor 11 are similarly supported.

I claim:

1. Apparatus for classifying flat ferrous sheets according to desired magnetic characteristics, comprising cooperating; upperand lower conveyors, said lower conveyor having a sheet-receiving portion and a sheetexiting portion, each of said conveyors including an endless belt trained over spaced rolls and disposed so that one end of the lower reach of said upper conveyor belt is closely spaced with respect to the upper reach of said lower conveyor belt at a portion of said lower conveyor intermediate said sheet-receiving and sheetexiting portions to form a throat therewith through which a sheet passes, said reaches diverging in a direction toward said sheet-exiting portion of said lower conveyor so that said throat enlarges in this direction, a first plurality of electromagnets supported along a path longitudinally of said lower reach and inwardly of said throat, and second plurality of magnets supported along and establishing a curved path longitudinally of said upper reach and inwardly of said throat, said curved path being in juxtaposition to said upper reach and the latter following said curved path, means for selectively energizing said first and second plurality of magnets, said sheet being attracted to said lower reach when said first plurality of magnets are energized and carried thereby to a desired location, and said sheet being attracted to said upper reach when said second plurality of magnets are energized and longitudinally curved to correspond to the curvature of said path.

2. The construction according to claim 1 wherein the curvature of said curved path is an amount that would not bend the sheet beyond its elastic limit, whereby said sheet beyond said curved path will resume its flat condition.

3. The construction of claim 1 wherein said upper reach extends along said sheet-receiving and sheetexiting portions of said lower conveyor, and magnets below said upper reach at such portions to attract and hold a sheet thereto.

4. The construction according to claim 3 wherein the upper reach in each of said portions is substantially straight.

5. The construction according to claim 1 wherein each of said first and second plurality of magnets is separately carried by a channel member, the web of each channel member being removably secured to the frame of said apparatus.

6. The construction according to claim 1 wherein said upper conveyor is vertically adjustable.

7. The construction according to claim 6 and including means for effecting said vertical adjustment at a plurality of places. 

1. Apparatus for classifying flat ferrous sheets according to desired magnetic characteristics, comprising cooperating upper and lower conveyors, said lower conveyor having a sheet-receiving portion and a sheet-exiting portion, each of said conveyors including an endless belt trained over spaced rolls and disposed so that one end of the lower reach of said upper conveyor belt is closely spaced with respect to the upper reach of said lower conveyor belt at a portion of said lower conveyor intermediate said sheet-receiving and sheet-exiting portions to form a throat therewith through which a sheet passes, said reaches diverging in a direction toward said sheet-exiting portion of said lower conveyor so that said throat enlarges in this direction, a first plurality of electromagnets supported along a path longitudinally of said lower reach and inwardly of said throat, and second plurality of magnets supported along and establishing a curved path longitudinally of said upper reach and inwardly of said throat, said curved path being in juxtaposition to said upper reach and the latter following said curved path, means for selectively energizing said first and second plurality of magnets, said sheet being attracted to said lower reach when said first plurality of magnets are energized and carried thereby to a desired location, and said sheet being attracted to said upper reach when said second plurality of magnets are energized and longitudinally curved to correspond to the curvature of said path.
 2. The construction according to claim 1 wherein the curvature of said curved path is an amount that would not bend the sheet beyond its elastic limit, whereby said sheet beyond said curved path will resume its flat condition.
 3. The construction of claim 1 wherein said upper reach extends along said sheet-receiving and sheet-exiting portions of said lower conveyor, and magnets below said upper reach at such portions to attract and hold a sheet thereto.
 4. The construction according to claim 3 wherein the upper reach in each of said portions is substantially straight.
 5. The construction according to claim 1 wherein each of said first and second plurality of magnets is separately carried by a channel member, the web of each channel member being removably secured to the frame of said apparatus.
 6. The construction according to claim 1 wherein said upper conveyor is vertically adjustable.
 7. The construction according to claim 6 and including means for effecting said vertical adjustment at a plurality of places. 